Split mortgage by income (UK) — a fair way to share costs
If one person earns more, a strict 50/50 split can feel unfair (or simply unsustainable). A proportional split uses take‑home pay to decide who pays what, so both people keep a more similar “leftover” each month.
What “split by income” means
A proportional split is simple: add both take‑home incomes together, then each person pays the same proportion of shared monthly costs as their share of income. If you bring home 70% of the household income, you cover 70% of the shared costs (mortgage + bills you treat as shared).
This is not advice — it’s a budgeting method that makes the trade‑offs explicit. You can still choose 50/50 or a custom split (like 66/33) if that better reflects your situation (deposit differences, childcare, etc.).
Step‑by‑step method
- Estimate your monthly mortgage payment from the loan amount, rate, and term.
- Add shared monthly costs (council tax, utilities, insurance, a maintenance buffer, and optionally groceries).
- Split the total shared cost using proportional / 50‑50 / custom.
- Check “leftover each” and stress tests (+1%, +2% and one‑income).
Worked examples (with real numbers)
These examples use the same calculation engine as the main calculator. Click “Open this scenario” to see the full breakdown and tweak inputs.